Figure 1.

Schematic of a catheter tip placed concentrically inside an artery. The discharge velocity through the catheter is much higher than the surrounding flow. The high velocity discharge tends to generate an ejector effect whereby the surrounding fluid is entrained into the jet flow enhancing both mixing and flow of the slow moving fluid. Q_b and Q_c are the flow rates of blood analog fluid and injected contrast, respectively; V_b and V_c are the corresponding velocities; D and d are the inner diameters of the artery and the catheter, respectively. The mixing length is the distance from the catheter tip at which contrast has formed a homogeneous mixture with the surrounding fluid.